The present invention relates to a disk-like recording medium, a disk recording apparatus and a disk recording method, and a disk playback apparatus and a disk playback method, and particularly to a disk-like recording medium, a disk recording apparatus and a disk recording method, and a disk playback apparatus and a disk playback method that make it possible to reproduce auxiliary information of a disk reliably.
As write-once or rewritable disks are spread, data replication of which is prohibited (for example contents data such as music data and video data protected by copyright or the like) may be illegally copied. On a DVD (Digital Versatile Disk), for example, a BCA (Burst Cutting Area) is provided to prevent illegal copying between disks.
The BCA provided on a DVD will be described with reference to FIG. 1. A BCA 2 of a DVD 1 (DVD-ROM (Read Only Memory) or DVD-RAM (Random Access Memory)) is irradiated with pulse laser light of a YAG (yttrium-aluminum-garnet) laser at a factory prior to shipment, whereby stripes (bar code) is formed along the innermost circumference by removing, in a radial direction, narrow stripes of reflecting film made of aluminum or the like formed on an inner side of the disk. The stripes show auxiliary information such for example as an ID number and other identification information and an encryption key. The BCA 2 is formed for about 330° along the innermost circumference of the DVD 1.
Data structure of data recorded in the BCA 2 is shown in FIG. 2.
The data recorded in the BCA 2 has a row of five bytes as one unit. A first one byte of the row of five bytes is a sync byte (SB) or a resync (RS). A BCA-Preamble is recorded in four bytes of a first row. The BCA-Preamble is data including only 0s. Four bytes of each row in a BCA data field is an information area or an EDC (error detection code). Four bytes of each row in an ECC (error correction code) area is error correction code. A BCA-Postamble is recorded in a last row.
When the data recorded in the BCA 2 is to be reproduced, a reproducing apparatus generates a clock on the basis of a reproduced signal of the BCA-Preamble part by means of a PLL (Phase Locked Loop), and performs demodulation and error correction by a predetermined method on the basis of the clock to thereby reproduce the data.
However, if the PLL loses synchronism in reproducing the data recorded in the BCA due to some defect, for example, the data cannot be reproduced until the PLL regains synchronism. This means that reproduced data is lost for a period when the synchronism of the PLL is lost.
Also, if a synchronization signal (sync) is lost once due to a defect or the like, data may be lost until a next synchronization signal is detected.
If the amount of lost data is larger than an error correction capability (that is, if there is a local major defect), data cannot be reproduced. The information recorded in the BCA 2 is ID information unique to each disk and the like. It may be related to the entire data on the disk (for example determine whether contents recorded on the DVD 1 may be reproduced or not). Therefore, high reliability is required for data recording and reproduction recorded in the BCA 2. In order to reduce the amount of lost data, a method of frequently inserting a synchronization signal for resynchronization is conceivable; however, such insertion of the redundant synchronization signal reduces the amount of data recordable in the BCA.